1. Field of the Invention
The present invention relates to a measuring system.
2. Description of the Background Art
It is known to scan the marks of an encoder disk to detect a specific position of a shaft, for example, the crankshaft or the camshaft of an internal combustion engine. The marks are indicated on the surface of the encoder disk. The encoder disk is attached to the relevant shaft and the marks are to be scanned with a stationary pickup. In this regard, in the pickup, for example, an inductive pickup, voltage pulses are induced by the marks passing by and are processed in a downstream evaluation circuit or a downstream control device, whereby the shaft rotational speed is calculated from the time intervals of the voltage pulses.
A device with which the rotational speed and the angular position of the shaft are determined in this manner is known, for example, from EP 01 88 433, which corresponds to U.S. Pat. No. 4,715,009. In this case, an encoder wheel with a plurality of angle marks is scanned and the obtained voltage is converted to a square wave voltage. The rotational speed information is obtained from the time intervals of similar angle mark edges. The angle marks must either be made very precisely, so that the intervals between similar angle mark edges are very precise, or the rotational speed can be determined only imprecisely.
DE-OS 30 18 496 discloses a method and a device for measuring an angle, in which an encoder wheel connected to a rotating shaft with a plurality of marks is scanned by a pickup, whereby to increase accuracy in a calibrating run first the intervals between the individual angle marks are measured, and said measured values are stored and taken into account in a subsequent evaluation process for measuring an angle.
DE 41 33 679 A1, which corresponds to U.S. Pat. No. 5,428,991 discloses a method for adapting mechanical tolerances of an encoder wheel, with a number of marks which are approximately equidistant and which are scanned by a pickup. The pickup supplies a pulse train whose time interval is measured and stored. The encoder wheel is connected to a rotating shaft of an internal combustion engine. A check is run whether the internal combustion engine is in the coasting mode. In a detected coasting mode, the second and the following time intervals are placed in relation to the first time interval.
An acceleration sensor is known from DE 41 09 217 A1. The acceleration sensor operates according to the spring-mass principle, whereby the weight is rotatably mounted. The restoring forces are generated by a spring, which is attached, on the one hand, to the weight and, on the other, to a holder rotationally fixed in relation to the weight. The change in position can be determined via a Hall element by a capacitive or optical method. The acceleration sensor can be provided with vibration damping, which is formed as eddy current damping or air damping. The weight is deflected proportionally to the acceleration against the action of the spring. The extent of the deflection is determined by the inert mass, the distance of the center of mass−center of rotation, and the spring constant of the spiral spring. In addition, a mechanical stop is provided which limits the deflection.
Furthermore, other acceleration sensors are known from DE 10 2998 060 191 A and DE 3520 928 A1.